西双版纳勐养自然保护区种植砂仁对重点保护植物的影响及对策

勐养保护区种植砂仁主要在沟谷雨林林下 .通过 2 5m× 1 0 0m典型沟谷雨林与6m× 40 0m砂仁种植地植物种类的比较分析 ,表明种植砂仁使雨林结构的B层受到影响 ,B、C、D、E层受到破坏 ,使 8种国家级保护植物可能流失 ,它们是A层的大果青冈和香籽含笑 ;B层的云南肉豆蔻、琴叶风吹楠、林生芒果和大叶木兰 ,D层的云南苏铁和E层的艹立句 艹弱薯等 .使 7种云南省省级保护植物可能流失 ,它们是C层 3种 ,D层 4种 .对策是依法严格保护核心区 .试验区保护植物相对集中地段和当地村民共同管理 .种植砂仁尽量留保护植物作遮荫树     

砂仁种植对热带沟谷雨林群落影响的研究

通过原始雨林与砂仁种植群落的比较 ,分析了在西双版纳地区沟谷雨林林下种植砂仁对沟谷雨林群落种类组成、结构、外貌和动态 ,以及幼树个体生长的影响 .沟谷雨林林下种植砂仁对雨林的生物多样性有较大的破坏 ,造成种植群落 70～ 90 %的物种流失 ,约 98%个体消失 .其中草本和灌木植物种类和个体基本全部消失 ,乔木植物种类损失 60～ 70 % ,个体损失 50～ 80 % .种植砂仁使群落垂直结构变得简单 ,分层明显 .种植后的群落仍保持雨林的外貌 ,但已不再是雨林群落 ,变成稳定性较差的次生林群落 .     

热带林下人工种植阳春砂仁的生长与果实产量动态

调查了西双版纳不同海拔热带沟谷雨林和次生林下的阳春砂仁生长和果实产量动态．结果表明,西双版纳热带林下阳春砂仁自身年龄增长、林下光照不足和旱季水分胁迫影响阳春砂仁果实产量。随种植期增加,阳春砂仁果实产量和成熟植株密度降低．当林下光照水平在全日照的35％以下时,阳春砂仁果实产量随林下日照水平变化呈线性增加(P<0．05)。沟谷下方阳春砂仁果实产量显著高于上方(P<0.05)。海拔600～1000m,由于阳春砂仁的主花期从干热季3～4月推迟到雨季5月,果实产量显著增加,沟谷雨林和次生林下阳春砂仁果实产量差异不显著。因此,在海拔800～1000m沟谷中轮歇地次生林下有计划种植阳春砂仁,代替在沟谷雨林下种植阳春砂仁,既能解决沟谷雨林下光照和当地旱季水分不足对阳春砂仁果实产量的影响,又有利于热带沟谷雨林的保护。     

西双版纳热带湿性季节雨林和次生林林下砂仁种植的比较研究

为保护热带雨林,改变现有砂仁栽培模式,探讨改雨林下种砂仁为次生林下种砂仁的可行性．比较研究了热带雨林和次生林下砂仁的生长状况和产量．砂仁种植对雨林生物量和生产力影响显著,对次生林的影响不显著．2种林下砂仁4类植株的密度和生物量的大小顺序均为壮株、衰老株、苗和笋．雨林和次生林下砂仁笋和苗的总数分别为衰老株数量的3．95和1．66倍,远多于衰老株数量,表明砂仁能够维持种群稳定．雨林下砂仁苗多为长势较弱的老苗,绝大多数最终不能生长成壮株．2种林下砂仁壮株密度和生物量差异不显著。但次生林下砂仁衰老株、苗和笋的密度和生物量显著高于雨林,表明次生林下砂仁更新比雨林下快．次生林下砂仁产量为78．068kg·hm^-2,略高于雨林．值得注意的是。砂仁产量很低,茎生物量比很高(0．6以上),果实生物量比极低(0．01),增产潜力较大．次生林的生物量低于雨林,透光率高于雨林。土壤水分含量与雨林接近,有利于砂仁的生长发育。可以在次生林下种植砂仁。     

热带林下人工种植阳春砂仁的生长与果实产量动态

调查了西双版纳不同海拔热带沟谷雨林和次生林下的阳春砂仁生长和果实产量动态.结果表明,西双版纳热带林下阳春砂仁自身年龄增长、林下光照不足和旱季水分胁迫影响阳春砂仁果实产量.随种植期增加,阳春砂仁果实产量和成熟植株密度降低.当林下光照水平在全日照的35%以下时,阳春砂仁果实产量随林下日照水平变化呈线性增加(P<0.05).沟谷下方阳春砂仁果实产量显著高于上方(P<0.05).海拔600～1000m,由于阳春砂仁的主花期从干热季3～4月推迟到雨季5月,果实产量显著增加.沟谷雨林和次生林下阳春砂仁果实产量差异不显著.因此,在海拔800～1000m沟谷中轮歇地次生林下有计划种植阳春砂仁,代替在沟谷雨林下种植阳春砂仁,既能解决沟谷雨林下光照和当地旱季水分不足对阳春砂仁果实产量的影响,又有利于热带沟谷雨林的保护.     

西双版纳热带季节雨林下种植砂仁干扰对雨林净初级生产力影响

 砂仁（Amomum villosum）为耐荫多年生草本,喜生于雨林林窗中,果实药用。在西双版纳热带季节雨林下广泛种植。为了通过提高林下光照水平来促进砂仁生长、增加产量,种植地雨林下的灌木及草本被清除,约60%～70%的乔木遭到疏伐,林冠盖度由85%～95%降低到55%～60%,雨林受到严重干扰。对3块原始热带季节雨林和3块受种植砂仁干扰雨林样地的净初级生产力（NPP）进行了测定和比较,原始雨林NPP（平均值±SE）为23.47±2.12 t·hm-2·a-1,其中各层次的NPP分别为：乔木层22.04±2     

西双版纳勐养自然保护区砂仁的分布现状和适宜地选择

通过实地调查和 6家重点农户砂仁地一年定期观察资料表明 ,砂仁集中分布在沟谷季节性雨林林下 ,在半常绿季雨林和季风常绿阔叶林下也有分布 .为发展山区民族经济和减小对热带山地森林的干扰 ,以海拔高度和单位面积产量作为砂仁种植适宜地选择标准 ,提出最适宜区是海拔 80 0～ 1 1 0 0m ,0 .0 667hm2 产干果 1 5kg以上 ;不适宜区是海拔1 30 0m以上 ,0 .0 667hm2 产干果 1 .9kg以下地区 ;此外 ,0 .0 667hm2 产干果 2～ 1 4.9kg的其它地区是适宜区 .最适宜区的国有林部分应加强管理 .     

西双版纳勐宋山区热带山地雨林的群落学研究

首次报道了云南西双版纳勐宋的热带山地雨林群落 ,该群落植物区系组成特殊 ,森林上层乔木组成中以古老的单室茱萸科 (Mastixiaceae)和紫树科 (Nyssaceae)植物为优势 ,亦富有木兰科 (Magnoliaceae)的长蕊木兰、云南拟单性木兰 ,红花木莲等系统发育上较原始的植物以及一些典型东南亚热带山地雨林群落的代表植物。通过对该热带山地雨林群落组成与结构的调查研究 ,认为该热带山地雨林可区分为沟谷和山坡 2个类型。沟谷群落类型以八蕊单室茱萸和大萼楠为乔木层优势种 ,可定义为八蕊单室茱萸—大萼楠林。山坡群落类型以云南拟单性木兰和云南裸花为优势 ,可定义为云南拟单性木兰—云南裸花林。     

粤东七目嶂自然保护区桫椤群落维管植物多样性研究

采用植物群落学、区系学等方法, 对保护区内桫椤群落及物种多样性、物种区系成分、生活型谱和群落结构等进行研究。调查表明: (1)群落范围内有46科66属78种的维管植物, 其中的蕨类植物有9科9属11种, 被子植物有37科57属67种。(2)生活型谱中以高位芽植物为主, 约占58%。(3)科和属的分布型均以热带分布型为主, 均超过65%; (4)群落垂直分层显著, 乔木层的树高所占比例最大的是在4—16 m, 约占77%; 灌木层最大是在0—2 m, 约70%; 草本层的各区间分布在0—0.4 m的比例比较大, 群落层次比较明显。乔木层和灌木层的平均高度均低于沟谷附近其他地段的植物群落, 很可能是沟谷特殊的生境和一些人为的干扰所致。(5)群落植物多样性较丰富, 物种丰富度、Shannon-Wiener多样性指数、均匀度指数、Simpson指数、Margalef指数均高于周边的风水林。加强对保护区内桫椤的生态监护, 在合适地段种植和栽培以扩大种群规模, 从而更有利于保护桫椤种群。     

砂仁种植对季节雨林土壤节肢动物群落结构影响的初步研究

为了探讨砂仁种植对热带季节雨林土壤节肢动物群落的影响,采用样地调查法对西双版纳勐仑自然保护区热带季节雨林及林下砂仁种植地土壤节肢动物群落进行了调查,2种生境、不同季节3次取样共获得土壤节肢动物3772个,隶属6纲23目,其中砂仁地中膜翅目(蚂蚁)、蜱螨目、半翅目为优势类群,占全捕获量的73．329％,而季节雨林中膜翅目(蚁类)、蜱螨目、鞘趔目和弹尾目为优势类群,占全捕量89．778％。2样地土壤节肢动物类群数、个体数和多样性指数的水平分布差异显示为季节雨林高于砂仁地,垂直分布显示季节雨林为土壤表层多于下层,表聚现象明显,砂仁地因受人为活动影响,其土壤节肢动物的垂直分布具有较大变化,出现下层高于表层的逆向分布;2样地土壤节肢动物群落季节变化趋势相近,均表现为干季高于雨季,其中砂仁地土壤节肢动物个体数在干热季最多,季节雨林个体数则在雾凉季最高。     

砂仁种植对热带雨林植物多样性的影响探讨

通过对各种不同状况的林下种植砂仁的热带雨林片断与同样类型的原始热带雨林的比较研究 ,探讨了砂仁种植对热带雨林植物多样性各个方面的影响。砂仁种植必须大量清除小树、林下幼树、灌木层植物 ,致使种植了砂仁的热带雨林片断的乔木下层及几乎整个的幼树、灌木层遭严重破坏 ,物种和个体大量流失 ,群落结构变得非常不稳定。由于热带雨林的更新主要依赖于其林下层的幼苗库 ,林下层的幼树、苗库被清除或破坏 ,热带雨林就难以自我更新 ,故林下种植砂仁的更大的潜在危害是使得热带雨林不能自我更新。种植了砂仁的热带雨林片断 ,物种和个体数的减少或流失 ,主要是直接的人为清除的结果 ,清除强度大 ,种类和个体减少就多。热带雨林下砂仁种植后 ,那些在原乔木层中占多数的只有 1～ 2个个体的脆弱种类 (种群 )将首先消失     

海南霸王岭热带雨林植被取样技术研究

借助地理信息系统软件的表格操作及邻体分析功能,以海南霸王岭自然保护区的沟谷雨林为例,探讨热带雨林的取样技术。结果表明,用种．面积曲线所获得的热带雨林的最小面积往往过大,而采用重要值．面积曲线所确定的最小面积则为4000m^2;无样地取样采用最近个体法,由种．点数曲线可以确定最少点数为119,而采用重要值．点数曲线,可以确定该雨林取样的最小点数为280。种．个体曲线表明,如果要获取多一倍的物种数,则所需调查的个体数应是原来的4倍。     

The impact of Amomum villosum cultivation on seasonal rainforest in Xishuangbanna, Southwest China

Integrating conservation goals with the sustainable use of tropical rain forests has received much attention in recent decades. Amomum villosum, a traditional Chinese medicinal herb, has been cultivated in the understory of seasonal rain forest for 40 years in Xishuangbanna, Southwest China. Cultivated area has reached 58.11 km² much of which is distributed within nature reserves. This practice has caused controversy on whether A. villosum cultivation would alter the structure and function of the primary forest. This study examined the effects of medicinal plant cultivation on seasonal rain forest by comparing plant diversity, biomass, litterfall and soil nutrients of primary rain forest with disturbed areas where A. villosum is cultivated. The results indicate that plant diversity, tree biomass, litter production and soil nutrients are significantly lower in the disturbed than in the primary rain forest. These results suggest that the cultivation of A. villosum affects the structure and function of the seasonal rain forest in Xishuangbanna.     

西双版纳热带雨林下砂仁拔除后的生态恢复

 种植砂仁（Amomum villosum）对西双版纳热带雨林植物多样性的影响引起了人们的关注。通过西双版纳热带雨林下种植的砂仁拔除后的生态恢复两年的研究工作,结果表明砂仁排除后：1）林下植物数量显著增加,超过同等类型的没种过砂仁的原始热带雨林;植物种类、物种多样性和均匀度都有大幅度增加,与原始热带雨林差别不大;群落组成成分仍向着热带雨林演替,优势种不明显,其中,草本和蕨类植物增加显著;2）林下植物生长速率在旱季与原始林差别不大,但在雨季可有较快生长;生物量在两年内可达到(636.1±43.4) g·m-2,超过原始林,特别是草本和蕨类植物生长较快;3）土壤含水量得到提高,与原始林相比差异不显著,并且,涵养水源的能力有所增加;深层土壤有机质的含量增加显著,速效磷含量需要更长时间的植被恢复才能有所提高,速效钾受淋洗作用的影响,地表有大量损失。文中最后讨论指出,热带林下砂仁实现斑块式的轮歇种植是协调保护与发展的较好方法,这在偏远少数民族地区有着较好的可行性。     

滇南热带雨林物种多样性的取样面积探讨

通过不同面积样方种数的比较、物种多样性指数等的计算和逐步扩大样地面积的调查, 本文研究了滇南热带雨林种数/面积关系、个体/种数关系、物种多样性及树种的频度分布规律, 认为滇南热带雨林群落学调查的最适取样(样方)面积是0.25 hm², 这个面积接近该类型热带雨林理论上的群落最小表现面积。 为能体现一个具体森林(群落)类型的基本的植物区系组成, 需设置4～5个这样的样方(总面积累计1 hm²以上)。从与世界不同地区热带雨林的比较亦可见,云南热带雨林有类似的树种频度分布规律,单位面积上的物种多样性比典型的东南亚低地热带雨林稍低,但比非洲的热带雨林要高。     

Clearance and fragmentation of tropical rain forest in Xishuangbanna, SW, China

Xishuangbanna, situated in the northern margin of the tropical zone in Southeast Asia, maintains large areas of tropical rain forest and contains rich biodiversity. However, tropical rain forests are being rapidly destroyed in this region. This paper analyzed spatial and temporal changes of forest cover and the patterns of forests fragmentation in Xishuangbanna by comparing classified satellite images from 1976, 1988 and 2003 using GIS analyses. The patterns of fragmentation and the effects of edge width were examined using selected landscape indices. The results show that forest cover declined from 69% in 1976 to less than 50% in 2003, the number of forests fragments increased from 6,096 to 8,324, and the mean patch size declined from 217 to 115 ha. It was found that fragment size distribution was strongly skewed towards small values, and fragment size and internal habitat differ strongly among forest types: less fragmented in subtropical evergreen broadleaf forest, but severe in forests that are suitable for agriculture (such as tropical seasonal rain forest and mountain rain forest). Due to fragmentation, the edge width was smaller in 2003 than that in 1976 when the total area of edge habitat exceeded core habitat in different forest types. The core area of tropical seasonal rain forest was smallest among main forest types at any edge width. Fragmentation was severe within 12.5-km buffers around roads. The current forest cover within reserves in Xishuangbanna was comparatively large and less fragmented. However, the tropical rain forest has been degraded inside reserves. For conservation purposes, the approaches to establish forest fragments networks by corridors and stepping stone fragments are proposed. The conservation efforts should be directed first toward the conservation of remaining tropical rain forests.     

MATING SYSTEM OF A TROPICAL RAIN FOREST TREE SPECIES

Canopy tree species are the dominant elements of the species-rich, fragile and endangered tropical rain forest ecosystems, yet little is known about the genetics of these species. We provide an estimate of the outcrossing rate in a population of Pithecellobium pedicellare, a large canopy tree in the tropical rain forests of Costa Rica. The outcrossing rate was high (t = 951 ± 0.021) and the pollen pool contributing to the progeny arrays used to measure outcrossing rate showed departure from homogeneity. The high outcrossing rate indicates that individuals scattered over a large area in this low density population could be bound with each other via outcrossing. However, despite a high outcrossing rate, the potential for inbreeding in this population is not negligible. We found a relatively large number of albino and chlorotic seedlings among the progeny arrays of several seed parents. Heterogeneity of pollen pool further indicates that the population, though widely outcrossed, may be structured. A more detailed study of mating systems in tropical rain forest trees may provide additional insights into the mating patterns of these trees. Such studies will be useful not only in understanding the dynamics of micro-evolutionary processes, but also in the conservation and management of tropical forest trees.     

High biogeographical and evolutionary value of Canary Island pine populations out of the elevational pine belt: the case of a relict coastal population

Aim Marginal populations are frequently neglected in static views of vegetation types, particularly when defining conservation reserves. The biogeographical and evolutionary importance of a marginal and endangered population of Pinus canariensis is addressed in this study to ascertain the need for conservation action. Diversity loss between adults and offspring and patterns of seed dispersal and recruitment were examined to provide evidence of recent degradation of marginal P. canariensis pinewoods. The scientific basis for the provision of sound conservation policies was investigated by elucidating the factors responsible for significant population structure. Location An isolated low‐density pinewood community confined to the Arguineguin ravine, in south Gran Canaria, Canary Islands. Methods Two cohorts, of centenary trees (those older than 100 years) and young recruits, respectively, were found in a detailed inventory of the pine population in the Arguienguin ravine. Chloroplast and nuclear microsatellites were compared to assess the levels of genetic diversity between adults and recruits. Spatial genetic structure and parentage analysis based on highly polymorphic nuclear and chloroplast microsatellites were examined to test limitations in seed dispersal. The underlying environmental factors that led to a clustering effect in the population were tested using point pattern methodologies. Results Centenary trees retain high levels of genetic diversity and effective population size, suggesting a wider extension of the pinewood forests in the past. A significant loss of genetic diversity was detected between adults and recruits. Pinus canariensis dispersal distances were among the longest ever reported for anemochorous species, suggesting that environmental factors account for recruit clustering. Cluster models showed that recruits tend to aggregate in dry streambeds, where soil and water accumulation favours establishment. Main conclusions Boundary populations of P. canariensis are subjected to fragmentation and reduction in effective population size as a result of human impact. Marginal populations were denser in the past and currently require specific conservation efforts. A severe reduction in genetic diversity compromises the future of present populations. Streambeds appear to play a major role in recruit establishment, but data suggest the absence of limitations to seed dispersal.     

Holocene mangrove dynamics and sea-level changes in northern Brazil, inferences from the Taperebal core in northeastern Pará State

A 450 cm sediment core from Taperebal, in the mangrove region of northeastern Pará State in northern Brazil has been studied through pollen analysis in order to reconstruct mangrove development and dynamics and to infer relative sea-level (RSL) changes during the Holocene. Six AMS radiocarbon dates, which provide a somewhat limited age control with some uncertainties, suggest early and late Holocene deposits interrupted by a hiatus between them. A patchy vegetation of coastal Amazon rain forest, restinga, salt marsh and some mangrove, which was dominated by Avicennia, covered the study area during the early Holocene period. The occurrence of an early Avicennia dominated mangrove phase has not been reported so far from other sites in northern Brazil. During the mid Holocene mangroves mostly replaced the former coastal Amazon rain forest, restinga and some salt marsh vegetation, reflecting the rise in the RSL. Rhizophora trees expanded markedly and Avicennia became rare. In the sediment core there is apparently a gap between the depths of 115 and 85 cm (possibly starting between 5900 and 5750 b.p.). The deposits above 85 cm are of modern age and were probably deposited during the last decades. This gap can be explained by the lowering of the RSL as is shown for other northern Brazilian coastal sites. The deposition of sediments during the last decades suggests that the modern RSL is high compared to other periods in the Holocene. Pollen data from these deposits show that Rhizophora trees dominate the mangrove forests, also indicating a high RSL.